1. Technical Field
This invention relates in general to multi-chip modules and, more specifically, to methods for repairing such modules by bonding out a module repair site using a repair solution generated during module testing.
2. State of the Art
As shown in FIG. 1, multi-chip modules (MCMs), comprising multiple dice carried on a printed circuit board (PCB) or other carrier substrate bearing circuit traces, are generally tested after being assembled, and those MCMs that pass testing are then shipped to customers. Those MCMs that fail testing are marked as such, typically by printing an "X" on the top of the "bad" (i.e., at least partially defective) dice that caused each MCM to fail testing. After being marked, any bad dice on a given MCM are disabled through various means including, for example, cutting conductive traces on the MCM to isolate the bad dice, or shorting conductive traces together to force a high-impedance condition on all inputs and outputs of the bad dice (e.g., by pulling the RAS* input of a Dynamic Random Access Memory (DRAM) permanently high).
Once the bad dice are disabled, known-good die (KGD) repair dice are attached to each failing MCM at an empty repair site. The failing MCMs with attached repair dice then proceed to a wire-bonding station, where an operator manually selects the wire-bonding pattern (also referred to as a wire-bonding "solution" herein) necessary to connect the repair dice to traces on the carrier substrate to replace the disabled bad dice. The repair dice are wire-bonded using the manually selected wire-bonding solution, and the repaired MCMs are then retested, with those repaired MCMs that pass the retesting proceeding on to shipping, and those repaired MCMs that fail retesting proceeding once again to repair or, alternatively, to scrap.
Because a wire-bonding machine operator manually selects a particular wire-bonding pattern for each MCM to be repaired, the process of repairing MCMs is subject to human error. Specifically, the operator generally selects the particular wire-bonding pattern to be used based on which dice are marked as bad (e.g., with the "X" described above), so the operator may make a mistake in observing which dice are marked as bad, or in selecting the appropriate wire-bonding pattern, or both.
Therefore, there is a need in the art for a method of selecting a wire-bonding solution for a MCM to be repaired that avoids the chance for human error associated with the conventional method described above.